<!DOCTYPE html>
<html lang="en" style="font-size: 10px;">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        @media screen and (max-width: 1200px) {
            body {
                background-color: red;
            }
        }
        @media screen  and (max-width: 800px){
            body {
                background-color: black;
            }
        }
        .box {
            width: 10rem;
            height: 10rem;
            background-color: black;
        }
    </style>
</head>
<body>
   <div class="box"></div> 
</body>
</html>